1. Field Invention
The present invention relates to an attaching device for removably attaching screening panels to the frame of a vibrating screen mechanism. Once the attaching device of this invention is installed on an existing vibrating screen mechanism, the screens may be removably attached to the attaching device by a positive locking system that does not bolt the screens to the attaching device or to the frame. The attaching device does not require special modifications to standard screen edges.
2. Description of the Prior Art
Mechanisms that are used to sort materials by screening are well known in the art. Such mechanisms normally are comprised of a frame to which is mounted a series of screens that are held in place by various methods of attachment. The most common method of attachment is by bolting the individual screens to a longitudinal support frame or grid. Replacing installed screening panels to change the opening size of the screen or to replace damaged screens is a labor intensive activity due to the time required to remove and replace bolts.
Newer methods of attachment have been developed. One such method is illustrated by U.S. Pat. No. 5,112,475 issued to Henry. In this system the existing support beams or grid that directly support the screen panels on a vibrating screen mechanism are removed and new support beams are installed. The new beams have pre-drilled apertures for attachment of a locking system. The locking system comprises a longitudinal channel member that is interposed between two adjacent screen panels. The specially formed edges of the screens are locked into an adjacent one of the sides of the longitudinal channel member. A second longitudinal T-shaped locking member is inserted between the legs of the channel member forcing the legs outwardly so that they engage the edge of the screen and lock laterally together. This system requires the replacement of existing support structure in order to attach the locking device to an existing vibrating mechanism. The portion of the T-shaped locking member inserted in the U-shaped member has sloping sides that engage sloping sides on the U-shaped member, which does not provide a positive lock in the upward direction. This system relies upon the side to side squeezing action to create a lock between the U-shaped member and the specially formed edges of the screens. Thus, a lock is only possible utilizing screens that have the preformed edge, and a positive lock will not be created with standard profile wire screen panels. The U-shaped channel of this system will not readily accept bolts for attachment to an existing frame of a vibrating mechanism. As mentioned previously, existing portions of the frame must be removed and new ones installed.
Australian patent No. AU-A-80172/91 issued to Lettela Pty. Limited, discloses screens that have modified edges to provide a cooperable connecting means for attachment to a locking system. This locking system also requires modification of the existing vibrating mechanism and requires that the edges of the standard profile wire screen panels be modified.
Notwithstanding the existence of such prior art screening attachment systems, it remains clear that there is a need for an attaching system which may be installed on existing vibrating screen mechanisms with little modification and which can use existing screens without modification. Such a system must provide a positive downward lock to ensure that the screens do not become loose, but must permit quick and early installation and removal of the screens.